This invention relates to perfluoroalkylether substituted aryl phosphines.
Because of their thermal stability, perfluorinated fluids have a great potential for use as engine oils, hydraulic fluids and greases. However, a serious drawback in their use results from the fact that certain metals are corroded by such fluids at temperatures of about 550.degree. F. and above in an oxidative environment.
In U.S. Pat. No. 3,393,151, issued to one of us as a coinventor on July 16, 1968, lubricants are disclosed that comprise a perfluorophenyl phosphorus compound. In U.S. Pat. No. 3,499,041 issued to one of us on Mar. 3, 1970, certain perfluoroarylphosphines are disclosed as being corrosion and oxidation inhibitors in polyfluoroalkylether polymeric fluids, while the phosphorus compounds described in these patents exhibit protective properties, they are only poorly soluble in perfluorinated fluids at low temperatures. Also, certain members of the classes of phosphorus compounds possess high volatility characteristics for long-term high-temperature applications. Because of these limitations, perfluorinated fluids containing such additives are not completely satisfactory for use in long-term, wide-temperature range (-100.degree. F. to &gt;550.degree. F.) application.
In U.S. Pat. No. 4,011,267 issued to two of us as coinventors on Mar. 8, 1977, certain perfluoroalkylether-substituted aryl phosphines are disclosed which have the following formula ##STR2## where R is a perfluoroalkylether group and n is 1, 2 or 3. Incorporation of these compounds in perfluoroalkylether fluids, e.g., fluids of the type disclosed in U.S. Pat. No. 3,393,151, inhibits the oxidation-corrosion of various metals with which the fluids come into contact. These additives also prevent decomposition of such fluids when exposed to a high-temperature oxidative environment. These additives exhibit better low-temperature solubility and lower volatility than the earlier known perfluoroarylphosphines. These compounds are, however, relatively expensive, thereby limiting their widespread usage. What is desired are compounds having the desirable characteristics of the compounds disclosed in U.S. Pat. No. 4,011,267, at a relatively lower cost.
It is an object of this invention to provide improved antioxidation-anti-corrosion additives for perfluorinated fluids.
Other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the accompanying disclosure.